Preparation And Property Characterization Of Bi₂O₃/YSZ Solid Electrolyte Material

Yttria stabilized zirconia?YSZ?is the most common electrolyte material currently used in the oxygen sensors and solid oxide fuel cell?Solid Oxide Fuel Cell,SOFC,a kind of energy conversion device which converts chemical energy into electrical energy?.It exhibits high oxygen ionic conductivity,excellent oxidative resistance and corrosion resistance,and nonreactive with electrode material.However,special heating equipment is needed when YSZ works as the oxygen sensor and the solid oxide fuel cells,because of its high operation temperature?typically>800??,which hinders the civilian development process.If the work temperature of the oxygen sensor and the cell can be decreased to the temperature?500-800??,it will not only can improve the stability of electrode,decrease performance requirements of batteries and cost,reduce thermal stress,and improve the stability of the battery and battery life,but also benefit to the scale and civilian of SOFC.Therefore,decreasing the operation temperature according to doping dopants,improving the molding method and optimizing the sintering process has been a hot spot in materials research.In this paper,different content of bismuth oxide was doped into YSZ material by chemical precipitation and wet ball milling method,then the wet blanks were sintered under different sintering process.The density,phase components,microstructure morphology and thermal shock resistance were analyzed to study the solid solution mechanism of Bi₂O₃-Y2O3-ZrO2 three-phase system.The optimum composition of the electrolyte material,the growth mechanism of one-dimensional rod like Bi₂O₃ material and the formation of YSZ slurry used for gel casting are discussed.It aims to promote the application research of SOFC electrolyte materials and gas sensitive ceramics.Bi₂O₃/YSZ composite powders can be obtained in the liquid phase by chemical precipitation method,and the Bi₂O₃ powders were produced by hydrolysis reaction and dehydration polycondensation.When crystallized in the liquid,the Bi₂O₃ powders trended to growth at the one-dimensional direction intensively and formed rod-like crystal,which was connected with the structure and surface energy of the crystal.The high temperature and concentration will enhance that case that is disadvantage of the preparation of Bi₂O₃/YSZ composite powders.When at the low temperature and mole percentage<1%,the Bi₂O₃ and YSZ in the composite powders are particle with small grain size,which are dispersed uniformly.When the ratio of raw material,temperature and dispersant was changed,one-dimensional rod like Bi₂O₃ can be obtained.The oriented attachment with interaction of Ostwald ripening was the possible growth mechanism of the one-dimensional rod-like Bi₂O₃.In the gel casting process,when the average particle diameter was 2.5?m,the amount of dispersant was 15vol.%,the solid content was 50vol.%,the stability and rheology of the slurry was the best.The viscosity was 510 mpa·s.When the initiator concentration was 1.24vol.%,the catalyst content was 1vol.%,the gel time was controlled in 20min,it can get the wet billet which was not easy to crack and had small deformation.It was found that the Bi₂O₃ can effectively reduce sintering temperature as a flux;Sintered at 1000?,t-ZrO2 can be induced into m-ZrO2 by Bi₂O₃ doped;With the increasing of Bi₂O₃ content,system shock resistance decreases,approaching a value;The thermal shock resistance of 2-3mol%Bi₂O₃-YSZ system is the best.